Push-button tuner for radio receivers



H. R. SHAW PUSH BUTTON TUNER FOR, RADIO RECEIVERS July 18, 1944.

Filed Sept. l5, 1942 55.558 mmc Patented July 18, 1944 PUSH-BUTTON TUNER FOR RADI() RECEIVERS Hubert R. Shaw, Drexel Hill, Pa., assigner to Radio Corporation of America, a corporation of Delaware Application September 15, 1942, Serial No. 458,346

(Cl. Z50-40) 11- Claims.

The present invention relates in general to a push-button tuner for radio receivers.

More specifically, it relates to a push-button operated receiver which permits the selection of any l kc. channel in a given band by means of push-buttons, the total number of which is considerably less than the number of channels contained in the band. For example, any 10 kc. channel in the broadcast band, 550 to 1550 kc., which contains 100 such channels, may be selected by means of only 21 push-buttons,

With present day push-button receivers there are usually provided from about five to ten pushbuttons for tuning in the more popular stations and an additional button for conditioning the receiver to be under control of the variable tuning condenser whereby other desired stations may be tuned in.

In accordance with the present invention the customary variable tuning condenser is dispensed with, as are also the tuning indicator dial and the parts associated with the condenser and dial for actuating the same. The tuning operation in the receiver according to the invention is accomplished by the selective connection of one of a plurality of semi-fixed condensers across a coil, or the selective connection of one of a plurality of coils across a condenser, or by the selective connection of both a coil and a condenser simultaneously.

It is therefore one of the objects of the invention to provide a receiver which is operated solely by push-buttons to select any 10 kc. channel in the broadcast, short-Wave or other bands.

Another object of the invention is to provide a receiver the circuit of which utilizes a plurality of frequency converters, the oscillator portions of which and the input to the receiver being tuned by the selective connection therein of a capacitor, a coil, or both.

Another object of the invention is to provide a receiver utilizing, for example, a double conversion superheterodyne circuit in which the number of hundreds kc., that is, to 15, for the broadcast band, is determined by the band of frequencies to which the receiver input is tuned and by the frequency to which the oscillator of the first converter is tuned and by the band of frequencies passed by the tuned circuits between the 1st and 2nd converters, and the number of lrc. in tens from 0 to 90 is determined by the frequency to which the oscillator of the 2nd converter is tuned and by the frequency to which the circuits following the 2nd converter are tuned.

Other objects of the invention are to improve generally the simplicity and efficiency of pushbutton receivers so that not only would they be reliable in operation but capable also of economical manufacture and assembly.

The novel features characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and mode of operation together with further objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a diagrammatic showing of the receiver circuit, and Fig.2 is a view showing the push-button arrangement in the front panel of the receiver.

Referring now particularly to Fig. 1 the circuit for illustrative purposes is shown to be of the double-heterodyne Vor double-conversion type. Radio signals picked up by the antenna Ant'. are transferred through the radio frequencyl transformer T to the signal input grid of the first converter tube D which may be a pentagrid or other suitable type. If amplification is desired before co-nversion a suitable amplifier may be interposed between transformer T and the converter. Connected across the secondary of the input transformer T is a bank (A) of semi-fixed condensers numbered 5a to 15a, each of which has one of its terminals connected to the high potential end of the transformer secondary and to the signal grid of the converter', the other terminals of said condensers being connected each by way of a separately actuated switch, shown at A5, Aia, A11, etc., to ground or the low potential end of the transformer secondary. The values of the several condensers of this bank are so chosen that each thereof in conjunction with the transformer secondary will constitute a tuned circuit which will pass a band of frequencies occupying a range of approximately kc. at differentfspectrums of the received band. Hereinafter this frequency range as well as others utilized in other parts of the receiver will be referred to as 100 kc. wide. It should be understood, however, that this range is approximate and may be more or less than 100 kc.

The first and second grids of the first converter are coupled in the conventional manner by the grid coil G1 and the feed-back coil P1 to constitute the first oscillator. In shunt to the feedback coil there is connected a second bank (B) of semi-fixed condensers numbered 5b to l5b, each of which lhas one of its terminals connected to the high potential end of the coil Pi,

the other terminals of said condensers being connected each by way of a separately actuated switch, shown at B5, Bio, B11, etc., to ground or the low potential end of the feed-back coil. The values of the several condensers of bank (B) are so chosen that the oscillator will produce a series of frequencies, with a 100 kc. separation between adjacent oscillator frequencies.

The corresponding switches of the banks A and B, as for example, A5--B5, A10-B10, etc., are adapted to be uni-controlled as indicated by the dotted lines connecting them. The uni-controlled connections are identified by the numbers 5 to 15 enclosed in circles, the circle signifying in each case that the corresponding pair of uni-controlled switches is adapted to be controlled by a pushbutton and the number representing the channel frequency in hundreds of kc. that the receiver will be tuned to upon operation of a particular push-button.

As shown in the table below, the selective operation of the switches in bank A to connect one of the condensers 5a to |5a will tune the input to the first converter to allow in each .case a pass band of 100 kc. to be transmitted. For example, operation of the switch A5 connects the condenser 5a into circuit and the carrier-frequencies from 500 to 590 kc. will be passed to the input grid of the rs't converter. Since the modulation frequencies of the first carrier-frequency of 500 kc. included in the band for switch A5 extend on either side of said carrier, between 495 and 505 kc., and the modulation frequencies of the last carrier-frequency of 590 kc. of this band extend on either side of said carrier, between 585 and 595 kc., the entire band of frequencies that will be passed by the input circuit to the rst converter will be from 495 to 595 kc. or a band of frequencies 100 kc. wide. Operation of the switch A111 connects the condenser 10a into circuit and the carrier-frequencies from 1000 to 1090 kc. or a frequency band 100 kc. wide will be passed to the first converter, etc. Similarly, the selective operation of the switches B5 to B15 in the bank B will tune oscillator #l of the rst converter in steps of 100 kc. from 3500 kc. for switch B5 to 4500 kc. for switch B15.

As mentioned above corresponding switches for banks A and B are controlled in unison so that in each 'case the resulting intermediate frequency, the range between 2910 and 3000 kc., will appear -1n the output circuit O1 of the converter D.

It is to be noted that only the tuned `circuit or circuits ahead of the 1st converter determine what band of frequencies reaches the converter and this band is 100 kc. Wide. The particular 100 kc. band of frequencies reaching the 1st converter will be determined by which push-button is depressed to tune the R. F. circuits, and the signal frequency it is desired to receive will be included in the band so selected. The 1st con.-

verter simply increases the frequency of all signals reaching its grid by an amount determined by the oscillator frequency which is in turn determined by the push-button depressed. By design, the band of frequencies passed from the 1st converter to the 2nd lconverter is 100 kc. wide and is the same band of frequencies for all pushbuttons.

The band-pass filter F1 in the output of the first converter is of known construction and is effective to pass the entire band of intermediate frequencies from 2910 to 3000 kc. to the signal control grid of the second converter H which may also be of the pentagrid type.

The first and second grids of this converter, as in the first converter, are coupled by way of coils G2 and Pz to constitute oscillator #2. Connected in shunt across the oscillator feed-back coil Pz is a third bank C of condensers numbered 00o, lc, 20c to 90e each of which has one of its terminals connected to the high potential end of the coil P2, the other terminals of said condensers being connected each by way of a separately actuated switch, shown at Coo, Cio, C20, etc., to ground or the low potential end of the feed-back coil. The values of the several condensers of this bank are so chosen that the second oscillator is adapted to operate at the frequencies indicated in the above table, from 2545 kc. for condenser 00e to 2455 kc. for condenser e, there being a 10 kc. separation between adjacent oscillator frequencies.

The beat frequencies resulting from the interaction between any one of the frequencies generated by oscillator #2 and the first intermediate band of frequencies 2910 to 3000 kc. will appear in the output Oz of the second converter, the values being indicated in the column under O2, it being noted that the beat frequencies in each case occupy a band kc. wide. Connected between the output of the second converter and the demodulator of the diode-triode tube RA is a second I. F. transformer F2 tuned to an intermediate frequency of 455 kc., the value com- 'monly chosen as the I. F. frequency in receivers of the superheterodyne, although any other I. F. frequency may be chosen if desired. As a consequence only a frequency of that value will be transmitted to the demodulator and audio amplifier tube RA, it being noted that the 455 kc. intermediate frequency is common to the several I. F. frequency ranges. If desired the audio frequency may be further amplified and then reproduced in the usual way through a loudspeaker, the block AF/LS representing the latter elements.

In Fig. 2 there is shown the front panel P of the receiver and a possible arrangement of the push-buttons, the push-buttons 5 to l5 in one row being adapted to control the switches A5 to A15 and B5 to B15 in banks'A and B, respectively,

`and the push-buttons indicated 00 to 90 in another row being adapted to control respectively the switches Coo to C90 in bank C.

Assuming now that it is desired to tune in a station operating at the channel frequency of 1000 kc., the button la in the top row representing the number of hundred kc. and the button 00 in the lower row representing the number of kc. in tens would be depressed. As a result the condenser l0 associated with the switch A10 in bank A will be connected across the input transformer secondaryto tune the same so that it will accept a frequency band between 1000 and 1090 kc, Simultaneously therewith the condensei- '#1 to produce a frequency of 4,000 kc.

the oscillator portion of the second converter to operate at a frequency of 2545 kc. The'mixing of this frequency with the bandof frequencies passed by the band-pass filter F1 will result in the frequency range from 365 to 455 kc. being present in the output of the second converter.v

However, since the second I. F. network Fzis tuned to pass only a frequency of 455 kc., the selected value for the intermediate frequency of the receiver, the other frequencies in the band will be attenuated, so that only the carrier-frequency of the desired station, namely, 1000 kc., will be demodulated and then amplified in the remaining portion of the receiver. Similarly, any combination of push-buttonsy in the first and second rows will produce the desired signal frequency in the output of the receiver; It will be understood of course that only one push-button in each row may be operated at any one time, the usual arrangement inpush-button receivers being employed to effect a release of a previously operated push-button upon actuation of a different push-button.

While the above described embodiment of the invention involves the selective switching inof condensers in each of the banks A, B and C, it will be understood of course that the same result is obtainable by the selective switching in of coils, preferably permeability tuned, or of a coil and condenser combination.

Although the invention has been described with reference to the broadcast band, it is to be understood that the invention may be applied to cover other bands, such as short-wave Mc bands, by utilizing a third converter and a third rowof push-buttons for tuning the circuits associated therewith in a manner similarly to that described in connection with the first converter. J

While there have been shown and described certain preferred embodiments of the invention, it will be understood that modifications and change may be made without departing from the spirit and scope of the invention, as will be understood by those skilled in the art.

What I claim is:

l. The method of operating a radio receiver to select any kc. carrier modulated channel within a given band of signal modulated radio carrier frequencies, which consists in receiving a narrow band of said frequencies which contains a plurality of 10 kc. channels including the desired channel, mixing said band of frequencies with a locally produced frequency to produce a narrow band of intermediate frequencies, which latter band is the same for any selected 10 kc. channel in the given band of frequencies, mixing said band of intermediate frequencies with a second locally produced frequency to produce aser:- ond narrow band of intermediate frequencies. which second band is the same for certain groups of 10 kc. channels and different for certain. other l0 kc. channel groups, and selecting from said second band of frequencies a single frequency which contains the signal modulations of the desired l0 kc. channel.

2. The method of operating a radio receiver to select any 10 kc. carrier modulated channel within a given band of signal modulated radio carrier frequencies, such as the broadcast band, by means of several banks of push-buttons, one bank representing the number of hundred kc. and another bank representing the number of kc. in tens/which consists in the selective operation vof one of the push-buttons ofthe hundred kc.

bank and the selective operation of one of the push-buttons in the tens bank, said first se- `lectiveoperation resulting in the reception of a narrow band of frequencies which contains a plurality of 10'kc. channels including the desired channel and in the mixing of said band of frequencies with a locally produced frequency to produce a narrow band of intermediate frequencies, which latter band is the same for any selected 10 kc. channell in the given band of frequencies,'the second selective operation resulting in the mixing of said band of intermediate frequencies with a second locally produced frequency to produce a second narrow band of intermediate frequencies, which second band is the same for certain groups of l0 kc. channels and different for certain other 10 kc. channel groups, and selecting from said second band of frequencies a single frequency which contains the signal modulations of the desired l0 kc. channel.

3. A radio receiver comprising a first frequency converter, a iirst set of reactors selectively operated to impress upon the input of said converter a narrow range of modulated radio carrier frequencies, a second set of reactors selectively operated to tune the oscillator portion of the first converter to a frequency such that the latter will mix with said frequency range applied to the converter input to produce a narrow range of intermediate frequencies, a second frequency converter, means for impressing said range of intermediate frequencies onto the input of the second converter, a third set of reactors selectively operated to tune the oscillator portion of the second converter to a frequency will mix with the range of intermediate frequencies to produce a band of frequencies of substantially constant width, adjacent such bands being in overlapping relation and the several bands containing a common frequency, means for selecting said common frequency, and means for demodulating, amplifying and reproducing said common frequency.

4. A receiver according to the invention defined in claim 3 wherein the several sets of reactors are constituted by condensers.

5. A receiver according to the invention defined in claim 3 wherein the several sets of reactors are constituted by coils.

6. A receiver according to the invention defined in claim 3 wherein the several sets of reactors are constituted by coil and condenser combinations.

7. A radio receiver comprising first and second frequency converters, a rst set of selectively operated reactors each of which is adapted to tune the input of the first converter to accept a different frequency range, a second set of selectively operated reactors each of which is adapted to tune the oscillator portion of the first converter to a frequency such that the latter will mix with each different frequency range applied to the converter input to produce the same range of intermediate frequencies, means for impressing said range of intermediate frequencies onto the input of the second converter, a third set of selectively operated reactors each of which is adapted to tune the oscillator portion of the secnd converter to a frequency which will mix with the range of intermediate frequencies to produce a band of frequencies of substantially constant width, adjacent such bands being in overlapping relationand the several bands containing a common frequency, means for selecting said common frequency. and mans for demodulating, ampli- -fying and reproducing said common frequency.

8.A A radio receiver as dened in claim '7 wherein the several sets of reactors are constituted by condensers and wherein a push-button controls the operation of corresponding condensers of the first and second sets, and another push-button controls the operation of each condenser in the third set.

9. A radio receiver as defined in claim 7 wherein the several sets of reactors are constituted by permeability-tuned coils and wherein a pushbutton controls the operation of corresponding coils of the rst and second sets, and another push-button controls the operation of each coil in the third set.

10. A radio receiver comprising first and second frequency converters, a rst set of semi-fixed condensers which are adapted to be selectively switched to tu e the input of the first converter to accept diierent frequency ranges, a second set of semi-xed condensers which are adapted to be selectively switched to tune the oscillator portion of the rst converter to a frequency such that the latter will mix with each different frequency range applied to the converter input to produce the same range of intermediate frequencies, means for impressing said range of intermediate frequencies onto the input of the second converter, a third set of semi-fixed condensers which are adapted to tune the oscillator portion of the second converter to a frequency which will mix with the range of intermediate frequencies to produce a band of frequencies of substantially constant width, adjacent such bands being in overlapping relation and the several bands containing a common frequency, means for selecting said common frequency, and means for demodulating, amplifying and reproducing said common frequency.

11. A radio receiver operated solely by pushbuttons comprising a rst row of push-buttons representing hundreds of kc. and a second row of push-buttons representing tens of kc., a first converter network under the control of the selective operation of any one of the push-buttons of the iirst row, and a second converter network under the control of the selective operation of any one of the push-buttons of the second row, said networks being so constructed and arranged that tl'ie frequency desired to be received is determined by the operation of one of the buttons in the rst row and one of the buttons in the second row.

HUBERT R. SHAW. 

